The proposed research is directed toward a determination of the lymphocyte surface structure of the various lymphocyte populations in the rabbit and in the human. This would be accomplished using mitogen and antibodies to these determinants as probes. Studies would be conducted on the surface of normal lymphocytes and related to the surface changes which occur during transformation as a result of immunization. Antigens specific to the various lymphocyte populations would be isolated, characterized and studied to evaluate their function. Monospecific antisera would then be developed for use in clinical evaluation of lymphocyte subpopulation. The presence of subpopulation specific antigens in the serum of normal individuals and individuals with various diseases would be studied. In vitro attempts would also be made to eliminate specific functional subpopulations of lymphocytes. BIBLIOGRAPHIC REFERENCES: Studies on the human T-lymphocyte population. IV. The isolation of T-lymphocyte antigens from peripheral lymphocytes. Owen, Frances L. and Michael W. Fanger. Immunochem. 13, 121, 1976. Studies on the human T-lymphocyte population. V. Isolation of T-lymphocyte antigens from human renal failure serum. Owen, Frances L., George M. Bernier, and Michael W. Fanger. Immunochemistry 13, 129, 1976.